Energetics

Thermochemistry

• physical transformations

• Energy released/absorbed in chemical reactions

• energy changes by chemical system during chemical reaction

Kinetic Energy

• energy of motion

• translational, rotational, vibrational

Temperature

• average kinetic energy directly proportional to temperature

• temperature increase = speed increase

• measures molecules movement

• measure of the average kinetic energy of particles

Celsius and Kelvin

• scales have the same size units

• 1 ºC change = 1 K change

Heat

• flow from hot to cold

• transfer of thermal energy

change in chemical energy

change in physical, chemical, nuclear state

Thermal Energy

• total kinetic energy of all particles of a system

• amount of energy dependent on the substance

Specific Heat Capacity

thermal energy needed to change the temperature of 1g of a substance by 1°C

Heat Capacity

• thermal energy needed to change temperature of a substance by 1°C

• regardless of mass

low specific heat capacity

easier to raise/lower its temperature

high specific heat capacity

harder to raise/lower its temperature

Q = mcΔT

• Q = heat

• m = mass

• c = specific heat capacity

• ΔT = change in temperature

Positive Q

• endothermic

• Heat gained by system

• temperature increase in system

• temperature decrease in surrounding

Negative Q

• exothermic

• Heat lost by system

• temperature increase in surrounding

• temperature decrease in system

Chemical Energy

• convert to kinetic energy (heat released)

• exothermic reaction - bonds break/reform

• Energy stored in intermolecular/intramolecular bonds

Origin of Organic Energy

comes from the sun

• Photosynthesis

• Biomass

• stored in Chemical Bonds

• Decomposition/Transformation

coal formation

1. plants die

2. dead plants burried under water and dirt

3. heat and pressure forms coal

oil and natural gas formation

1. sea plants/animals die and covered by layers

2. burried deeper

3. heat and pressure turns it into oil

Hydrocarbons

• chemical energy stored in them released as heat

• fossil fuels composed of hydrocarbons